U.S. Pat. No. 4,481,341, EP-A-661349 and U.S. Pat. No. 5,525,425 describe silicone resins which display a glass transition temperature, softening point, or melting point. These silicone resins can be used as encapsulation materials for hydrosilylation catalysts. To prepare such encapsulated catalysts, the silicone resins are dissolved in an organic solvent, and a hydrosilylation catalyst is added. The encapsulated hydrosilylation catalysts are obtained, for example, by removing the solvent and subsequently powdering the product, or by spray-drying the catalyst-containing silicone resin solution. With the aid of these encapsulated catalysts, one-component addition-crosslinking silicone compositions can be prepared.
The disadvantage of these encapsulated catalysts is that siloxane particles with different morphological structures cannot be synthesized using different siloxane units. It is therefore not possible to produce core/shell structures or to adjust the surface composition in a specific manner, and thus it is not possible to modify the compatibility or dispersibility of the encapsulated catalyst particles in the silicone composition by varying the particle surface composition. There is likewise a risk that the encapsulated catalyst, owing to the temperature increase during compounding, is liberated very quickly after the softening point or glass-transition temperature of the encapsulant has been reached, causing the silicone composition to crosslink prematurely during compounding.